A dealer would probably be the easiest way to get the paint codes. Any paint shop can mix the colors if they have the codes.
Your problem is going to be that the paint won't match after 11 years. The sun has faded what is on the coach and the new stuff will match the original, not the faded version. I have factory touch up paints for my 2004 and the only one that still matches is a jet black. The other three shades of tan and gold aren't even close
2004 American Tradition; 2014 Buick LaCRosse
Homebase in the Ocala Nat'l Forest near Ocala, FL